Some microelectronic devices have metal layers on the die attach surfaces of their substrates, to provide low resistance electrical or thermal connections. Copper is a desirable element for the metal layers, due to copper's high electrical and thermal conductivities. However, copper on the die attach surfaces of the substrates presents contamination, oxidation, and corrosion issues. Integration of copper layers on the die attach surfaces has been challenging to integrate into fabrication flows for the microelectronic devices.